Oscillator circuit



Jan. 10, 195@ H. KLEMPERER OSCILLATOR CIRCUIT Filed Jan. 19, 1946 C.source NUkEQm Patented Jan. 10, 1950 UNITED STATES PATENT ()FFICEOSCILLATOR CIRCUIT Hans Klemperer, Belmont, Mass, assignor to RaytheonManufacturing Company, Newton, Mass, a corporation of DelawareApplication January 19, 1946, Serial No. 642,402

8 Claims.

This invention relates to electrical circuits, and more particularly tohigh-frequency oscillating circuits.

An object of the invention is to devise a highfrequency oscillator orinverter using a gas tube.

Another object of the invention is to devise a high-frequency oscillatorcapable of delivering a relatively large amount of power.

A further object of the invention is to provide a high-frequencyoscillator which utilizes a mercury pool arc-discharge tube as the maininverter or oscillator element, and in which a tuned circuit is thefrequency-determining element.

A further object of the invention is to devise a high-frequencyoscillator utilizing a high-vacuum power triode with a gas tubeancillary thereto for the purpose of increasing the power output of saidoscillator.

Another object is to provide a means whereby a gas tube may be used inan oscillating circuit, such as is ordinarily used only for ahigh-vacuum tube.

The foregoing and other objects of the invention will be best understoodfrom the following description of some exemplifications thereof,reference being had to the accompanying drawing, wherein:

Fig. 1 is a schematic circuit diagram of one form of the invention; and

Fig. 2 is a detailed circuit diagram of a modification.

Referring to Fig. l, at I there is shown a controlled discharge tube.This is preferably a gasfilled tube of the controlled ignition type,which contains an anode 2 and a cathode 3, preferably of the mercurypool type. Anode 2 is connected through resistor A to the positiveterminal it of some suitable direct current source of high potential,such as 4000 volts for example, the negative terminal [4 of said sourcebeing grounded as shown. An inductance 5 in parallel with a condenser 6is connected from the cathode 3 to a conductor 1 which is grounded asshown, being thereby connected to the negative terminal of the directcurrent source. Inductance 5 serves as the primary of an outputtransformer, the secondary coil 8 being inductively coupled toinductance 5. The ends of coil 8 are connected to some suitable outputdevice or load 9.

Tube I is provided with a suitable igniting or control electrode i l forthe cathode 3. Although this igniter is of any suitable kind, itpreferably is of the electrostatic type as described in Spencer patent,No. 2,290,897, dated July 28, 1942.; Such 2 insulated from the cathodepool by a thin glass layer. In order to supply igniting impulses toigniter ID, a source of alternating current H of high frequency, forexample 1.5 megacycles, is connected, through resistor l2, between theoathode 3 and its associated igniter it.

The values of inductance 5 and condenser 6 are made such that these twoelements form a parallel resonant circuit at the frequency of A. C.source ll. When the source ll reaches a certain point in its cyclicalvariation, igniting electrode [0 reaches the required potential withrespect to the cathode 3 and an auxiliary arc is formed between theigniting electrode and the cathode, this being followed within amicrosecond by the formation of the main or controlled arc between anode2 and cathode 3. The establishment of the main arc in tube l causesdirect current to flow through circuit 5-6, which is in series withcathode 3, exciting the tuned circuit 56 into oscillations at itsresonant frequency. These oscillations serve to produce alternatingcurrent in the plate-cathode circuit of the tube, and the main arc intube I goes out when the potential of the anode 2 of tube i goesnegative with respect to its cathode 3. The tube does not immediatelyre-fire at this time because the voltage of the igniting electrode withrespect to the cathode has fallen to a value insufficient to maintain asupply of electrons. In tubes of the pool-cathode arc type, such as tubeI, within a few microseconds after extinction of the arc thedeionization in the vicinity of the cathode is great enough so that therequired electron emission, necessary to establish the arc between anodeand cathode, is not reestablished by reapplication of positive anodevoltage, provided of course that the potential of the igniting electrodewith respect to the cathode is not sufiicient to re-fire the tube atthis time. Since the circuit 56 is resonant at the frequency of sourceH, the oscillatory current in circuit 5-6 will have the same frequencyas does that of source ll, so that when source H again causes apotential sufficient for ignition to be applied to igniting electrodeill, the anode will have a positive potential with respect to thecathode and the arc will again be triggered, firing the tube. The aboveextinction process will then be repeated, and the ignition-extinctionprocess will be repeated at the frequency to which circuit ii- 5 istuned, producing oscillations of that frequency in coil 5, which may betaken off by coil 8 and utilized by load 9. The oscillation frequency isdetermined by the resonant frequency of tuned an igniter is generally aconductor separated and 55 circuit 5-6, since the anode must always havea certain positive potential with respect to the oathode in order forthe tube to fire, and the relative anode potential, as stated above, isdependent upon the oscillatory voltage in circuit 5-6. Because theoscillation frequency of the oscillator is determined solely by thetuned circuit, waves approximating pure sine waves are readilyobtainable from this circuit. Also, because the frequency of arcdischarges in tube 1 may be made very high, due to the extremely shortdeionization time of such tubes, very high frequency oscillations, onthe order of 1.5 megacycles, for example, may be obtained in thiscircuit, and relatively high amounts of power may be obtained at theexpense of only a low-power oscillator I I, since tube I may have a highcurrent-carrying capacity.

Referring now to Fig. 2, a high-vacuum thermionic tube is shown at l 5,this tube having plate l6, grid 11, and cathode l8. Plate I6 isconnected through high-frequency choke l9 to the positive terminal 28 ofa suitable direct current source. Cathode I8 is connected to thenegative terminal 2! of the direct current source, and is heated to thetemperature of thermionic emission by any suitable heating means, notshown. The tube I5 is connected in a Hartley oscillator circuit, theplate l6 being connected to one end of inductance coil 22 by means ofconductor 23 and the grid H to the opposite end of said coil by means ofconductor 24. A condenser 25 is connected across coil 22 to provide theresonant or tank circuit. Interposed in conductor 23, between plate l6and the plate end of coil 22, is a condenser 26 which serves tostabilize the frequency of oscillation of the oscillator. Interposed inconductor 24, between grid l1 and the grid end of coil 22, is agrid-blocking condenser 21, and between the grid side of this condenserand cathode I8 is a grid-leak resistor 28. This arrangement ofgrid-blocking condenser and grid-leak resistor acts to limit theamplitude of oscillation by making the potential of the grid I7 negativeas soon as oscillation commences. Cathode i8 is connected to anintermediate tap on coil 22 by means of conductor 29. Load 3| issupplied with alternating current from the oscillator by means of coil30, which is inductively coupled to coil 22 of the tank circuit.

A controlled discharge tube 32 is provided. This is a tube which isexactly the same in structure as tube 1 of Fig. 1, having anode 33,cathode 34, and igniting or control electrode 35. Anode 33 is connectedto positive terminal 20 of the D. C. source by means of lead 35, ahigh-frequency choke 3! being interposed in this lead as shown. Anode 33of tube 32 is coupled to the anode end of coil 22 by means of acouplingcondenser 38. Cathode 34 of tube 32 is connected, by means oflead 39, to conductor 29, and therefore also to the intermediate tap oncoil 22. Igniting electrode 35 is connected, through a phase-shiftnetwork 40, to the lower (grid) end of coil 22 by means of conductor 43.Network consists of a resistance 4| and a condenser 42 connected inparallel.

High-frequency oscillations are generated by tube l5 and its associatedcircuit, and appear across coil 22 of the tank circuit. A portion of thealternating voltage appearing across coil 22 is applied, by means ofconductors 33 and 43, between the igniting electrode 35 and cathode 34of tube 32. When the igniting electrode 35 reaches the requiredpotential with respect to the cathode 34, an auxiliary are between theigniting electrode and the cathode is termed, Wh G is followed within amicrosecond by the formation of the main or controlled are between anode33 and cathode 34, provided anode 33 has a certain positive potentialwith respect to cathode 34 at that instant. This main arc isextinguished as a result of the alternating current or oscillatorycurrent which appears in coil 22 and which is applied between anode 33and cathode 33. The arc is extinguished when the anode attains anegative potential with respect to the cathode, and is not immediatelyreestablished because the igniting electrode 35 does not have the properignition potential with respect to the cathode. The igniting electroderegains control of the tube an extremely short time after the arc goesout, due to the very short deionization time of the tube. When the anode33 again reaches a positive potential with respect to the cathode, thetube is again in condition for triggering and is triggered when theigniting electrode 35 reaches the required potential. The process offiring and extinguishing of the tube continues at a frequency orperiodicity determined by the resonant frequency of tank circuit 22, 25,because it is this tank circuit which determines the relative potentialsof the anode and cathode and also of the igniting electrode.

When the tube 32 is fired. or when the arc is triggered therein, directcurrent pulsations of almost rectangular waveform flow from the directcurrent source 2!], 2! through the anodecathode arc path of tube 32.Since anode 33 is connected through condenser 38 to one end of coil 22and since cathode 34 is connected by means of lead 39 to an intermediatetap on said coil, these direct current pulsations which flow throughtube 32 are effectively applied across the tank circuit of theoscillator. Due to the fact that the igniting voltage for tube 32 isobtained from the same tank circuit, the direct current pulsationsflowin through arc tube 32 will be in such phase relation to theoscillations produced by tube l5 that they will in effect provide aseparate source of current in parallel with the tank circuit which willboost the power obtainable from the oscillator tube. A tube of thecontrolled discharge type, such as tube 32, may be used to goodadvantage with a highfrequency oscillator to boost its power output,because the time required for effective deionization, after the anodevoltage drops to zero and the main arc goes out, is so extremely short.Phase-shift network 4!) establishes the phase of the arc dischargethrough tube 32 with respect to the oscillations of tube 5 5, and theimpedance values of said network may be varied to vary the relativephase of the impulses supplied to load 3| by gas tube 32, and thereforethe effective amount of power boost supplied to oscillator load 3! bysaid gas tube.

Of course, it is to be understood that this invention is not limited tothe particular details as described above, as many equivalents willsugest themselves to those skilled in the art. For example, any desiredtype of oscillatory circuit may be used in Fig. 2 instead of the oneshown, and other types of frequency-stabilizing means andamplitude-limiting means may be used if desired, or these latter meansmay both be dispensed with if desired. Other means than that shown forcoupling the gas tube to the oscillatory circuit in Fig. 2 may be used.If desired, plate 16 may be connected to coil 22 at a point spacedslightly from the extreme upper end of said coil, while plate 33 may beconnected to the extreme upper end of said coil. Various othervariations will suggest themselves. It is accordingly desired that theappended claims be given a broad interpretation commensurate with thescope of this invention within the art.

What is claimed is:

1. In an electrical circuit, a self-sustaining oscillator, a resonantoutput circuit including a coil having an intermediate tap connected asa part of said oscillator, an electrical space discharge device of theignition type fed by said oscillator and having a cathode, an anode, andan igniting electrode, means connecting said anode to one end of saidcoil, means connecting said electrode to the opposite end of said coilthrough a phasev shifting circuit, and means connecting said cathode tosaid intermediate tap of said coil.

2. In an electrical circuit, a thermionic tube having plate, grid, andcathode elements, a source of direct current, means connecting saidsource between the plate and cathode of said tube, a condenser-tunedcoil connected between said plate and grid elements, and meansconnecting said cathode to an intermediate tap on said coil, wherebysaid tube is connected as an oscillator and an oscillatory voltage isproduced in said coil, an electrical space discharge device of theignition type having a cathode, an anode, and an igniting electrode,means connecting said anode to one end of said coil, means includingphase-shifting means connecting said electrode to the opposite end ofsaid coil, means connecting said latter cathode to said intermediate tapof said coil and thereby also to said source, and means connecting saidanode to said source.

3. In an electrical circuit, an oscillator, a resonant output circuitincluding a coil connected as a part of said oscillator for supplying anoscillatory voltage of a predetermined frequency to a load, anelectrical space discharge device of the ignition type in addition tosaid oscillator and fed thereby having a cathode, an anode, and anigniting electrode, means connecting said cathode and anode to spacedpoints on said coil, and means connecting said electrode to a thirdpoint on said coil, the relative locations of said points being suchthat said device is ignited by said 05- cillatory voltage to therebysupply periodic pulsations of said predetermined frequency to said coilto reinforce the oscillatory voltage supplied to said load.

4. In an electrical circuit, a thermionic tube having plate, grid, andcathode elements, a condenser-tuned coil connected between said plateand grid elements, means connecting said cathode to an intermediate tapon said coil, whereby said tube is connected as an oscillator and anoscillatory voltage of a predetermined frequency is produced in saidcoil, an electrical space discharge device of the ignition type having acathode, an anode, and an igniting electrode, means connecting saidanode through a condenser to one end of said coil, means connecting saidelectrode to the opposite end of said coil, and means connecting saidlatter cathode to said intermediate tap of said coil, whereby saiddevice is ignited by said oscillatory voltage to thereby supply periodicpulsations of said predetermined frequency to said coil to reinforcesaid voltage.

5. In an electrical circuit, an oscillator, a resonant output circuitincluding a coil connected as a part of said oscillator for supplying anoscillatory voltage of a predetermined frequency, in addition anelectrical space discharge device of the ignition type having a cathode,an anode, and an igniting electrode, means connecting said anode througha condenser to a first point on said coil, means connecting said cathodeto a second point on said coil, and means connecting said electrodethrough a phase-shifting circuit to a third point on said coil, therelative locations of said points being such that said device is ignitedby said oscillatory voltage to thereby supply periodic pulsations ofsaid predetermined frequency to said coil to reinforce said voltage.

6. In an electrical circuit, an oscillator, a resonant output circuitincluding a coil having an intermediate tap connected as a part of saidoscillator, an electrical space discharge device of the ignition typefed by said oscillator and having a cathode, an anode, and an ignitingelectrode, means connecting said anode through a condenser to one end ofsaid coil, means connecting said electrode through a phase-shiftingcircuit to the opposite end of said coil, and means connecting saidcathode to said intermediate tap of said coil.

7. In an electrical circuit, an oscillator comprising a first spacedischarge device and a resonant output circuit including a coil havingan intermediate tap connected as a part of said oscillator, a source ofdirect current, a second space discharge device of the ignition typehaving a cathode, an anode, and an igniting electrode, means connectingsaid anode and cathode across said source, means connecting said anodethrough a condenser to one end of said coil, means connecting saidelectrode to the opposite end of said coil, and means connecting saidcathode to said intermediate tap of said coil.

8. In an electrical circuit, an oscillator, a resonant output circuitincluding a coil having an intermediate tap connected as a part of saidoscillator, a source of direct current, an electrical space dischargedevice of the ignition type fed by said oscillator and having a cathode,an anode, and an igniting electrode, means connecting said anode andcathode across said source, means connecting said anode through acondenser to one end of said coil, means connecting said electrodethrough a phase-shifting circuit to the opposite end of said coil, andmeans connecting said cathode to said intermediate tap of said coil.

HANS KLEMPERER.

, REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,947,093 Knowles Feb. 13, 19342,228,276 LeVan Jan. 14, 1941 2,251,877 Hagedorn Aug. 5, 1941 72,287,542 Vang June 23, 1942 2,314,739 Shepherd Mar. 23, 1943 2,351,439Livingston June 13, 1944 2,390,659 Morrison Dec. 11, 1945 OTHERREFERENCES Terman, Radio Engineering," 2nd edition. page 349.

